1. Field of the Invention
The present invention relates to a forming method of a thin film, a producing method of a semiconductor device and a substrate processing apparatus, and more particularly, to a technique for forming an oxide film on a semiconductor wafer (“wafer”, hereinafter) by an ALD (Atomic Layer Deposition) method in a producing method of a semiconductor integrated circuit.
2. Description of the Related Art
In recent years, as the density of a semiconductor DRAM device is enhanced and the number of multi-layered wirings is increased, it is required to form a film at a lower temperature, and a capacitor material having excellent surface flatness, excellent recess embedding properties, excellent step coverage and a high dielectric constant (k) is required. Materials such as HfO2 (k=30) and ZrO2 (k=25) are used as a capacitor material having a higher dielectric constant than the conventional Si3N4 (k=7). There are a sputtering method, an MOCVD (Metal organic CVD) method and an ALD (Atomic layer deposition) method as an HfO2 film forming method, but the ALD method capable of forming a film at a low temperature and having excellent step coverage recently gains the spotlight, and the development thereof is pursued energetically.
When these materials alternately flow into a reaction chamber to form the HfO2 film, there is a problem that if a pattern wafer having a trench structure is used, the step coverage is deteriorated because a film thickness is reduced at a central portion of the wafer, and coverage of the HfO2 film is deteriorated (called “loading effect”) depending upon the number of pattern wafers loaded in one batch. If the supply amount or supply time of a hafnium material is increased, the step coverage and the loading effect can be improved. However, throughput is deteriorated due to the increase in the film forming time, and COO (Cost of ownership: producing cost per one wafer) is increased due to the increase in the cost of material as a result of increased amount of the material consumed.
It is preferable that a metal material used for the ALD film forming method has appropriate chemical stability and high reactivity. It is preferable that organic compound has tertiary alkoxide or secondary alkoxide (MHn[OCR1R2R3]m-n or MHn[NR4R5]m-n as a ligand: wherein M represents a metal including one of an aluminum atom, a titanium atom, a zirconium atom, a hafnium atom, a tantalum atom, a ruthenium atom, an iridium atom and a silicon atom; m is a stable valence of the metal; n is an integer of 0 to 2 (n is equal to 0 when M represents an atom other than silicon); and R1 to R5 represent an alkyl group which has a carbon number of 1 to 4 and which may have ether binding at an intermediate portion).
Examples of hafnium materials are an Hf organic material such as Hf(O-tBu)4 (Tetra-ter-butoxyhafnium: Hf[OC(CH3)3]4), Hf(MMP)4 (Tetrakis (1-methoxy-2-methyl-propoxy) hafnium: Hf[OC(CH3)2CH2OCH3]4), TDEAHf (Tetrakis(diethylamino)hafnium: Hf[N(C2H5)2]4, TEMAH (Tetrakis(ethylmethylamino)hafnium: Hf[N(CH3)(C2H5)]4) and a chloride material such as HfCl4. In the case of silicon, in addition to the above-described ligand, hydrogen is also a preferred ligand if the number thereof is two or less. As an oxidant, ozone (O3) or plasma-excited oxygen is used.
Also when a SiO2 film is formed by the ALD film forming method like the HfO2 film, a chloride material such as SiCl4 or a Si organic material such as Si(MMP)4 (Tetrakis (1-methoxy-2-methyl-propoxy) silicon: Si[OC(CH3)2CH2OCH3]4) or TDMAS (Tris (ethylmethylamino) silicon: SiH[N(CH3)2]3) is used as a silicon material, but like the HfO2 film, there are a problem that the step coverage at the trench portion is poor and a problem with the loading effect.